Today, cellular radio networks are widely used by private and business users. Such networks typically provide a full duplex point-to-point voice communication service between a calling and a called communication partner. A service becoming popular in cellular radio networks is the Push-to-Talk service. PTT calls are half duplex one-to-one or one-to-many communications: while one person speaks, the other one or more persons must listen. The right to speak is granted by pressing a push-to-talk button on a first come/first serve basis. The PTT service allows communication with a dedicated group of people. A PTT group is defined by a subscriber of the PTT service with respect to a PTT server. The group is permanently stored and exists also after the communication between the group members is finished.
US 2004/0 249 949 A1 describes a method for distributing PTT voice and multi-media messages to communities of subscribers, using a definition of PTT groups. First, a PTT group of subscribers is created in an application server (=AS), either by one of the members or by a content provider server. Then, the subscribers register their interest in receiving PTT messages related to the created group, for example by joining a Session Initiation Protocol (=SIP) related to that group. Finally, the content provider server sends a PTT message destined to the PTT group, the message comprising voice and/or multimedia information, such as, e.g., news, stock quotes, sport updates, weather or commercial information. The message is received by the AS, which distributes it to the registered subscribers of the PTT group using its definition of the PTT group.
Further communication services are known that support contacts with other people. For example, US 2004/006548 A1 describes a server of a telecommunication network, wherein the server contains a data base having information on persons looking to meet other persons. Using telephones, users can input information both with regard to a person looking to meet another person and of a desired person. The server receives such personal information, stores it in the data base and compares the person information with the data stored in the data base to find persons, the information of whom complies with the received information on the desired person. The server determines a list of such persons and transmits it to the requesting telephone. The list can be shown on the display thereof. On the telephone a selection of a person in the transmitted list can be made and information on the selected person is transmitted to the server. The server establishes a telephone connection between the telephone of the person looking to meet another person and the telephone of the selected person.